The present invention relates to a dental system for treatment of periodontal pockets using laser light and having a handpiece with an optical fibre for directing laser light towards a target tissue area to be treated.
It is known to utilise laser light for treatment of periodontal pockets.
During treatment laser light heats plaque by illumination thereby destroying living cells in the plaque so that a subgingival infection is stopped by laser treatment.
Lasers that operate at a wavelength that is moderately absorbed in water are used for this treatment. When the laser power density (W/mm2) at illuminated cells is sufficient, cellular water is heated by energy absorption causing a temperature rise in the cell that destroy heated cells.
During treatment, it is essential not to heat or damage surrounding tissue. Residual heat may affect the nerve of the tooth causing pain to the patient and/or may cause tissue to char and become necrotic. Thus, it is desirable to minimise transmission of conducted heat to underlying and surrounding tissue.
It is therefore desired to accurately control the amount of light energy transferred to plaque, calculus, tissue to be incised, etc, to be treated. The amount of energy must be sufficient for effectively treating matter, such as plaque, calculus, tissue, and, simultaneously, the amount of residual energy heating surrounding tissue must be too low to heat the tissue.
It is an object of the present invention to provide a denial system for treatment of periodontal pockets using laser light for laser surgery, such as laser gingivectomy, periodontal pocket curettage, etc, without heating surrounding tissue.
According to a first aspect of the invention, the above-mentioned and other objects are fulfilled by a dental system for treatment of periodontal pockets using laser light, comprising a handpiece for directing laser light and a coolant spray towards a target area to be treated. The handpiece comprises a housing with an input end and an output end and holds an optical fibre duct for receiving and holding an optical fibre and extending within the housing from the input end to the output end. During operation of the system, an optical fibre with a fibre output end for emission of the laser light is positioned in the optical fibre duct. Further, the optical fibre duct may hold a seal that is adapted to receive and hold the optical fibre in water tight engagement with the optical fibre duct. The housing also has an air duct for transmission of compressed air and extending within the housing from the input end to the output end and a water duct for transmission of water and extending within the housing from the input end The water duct leads into the optical fibre duct within the housing between the output end and the seal so that water flowing through the water duct leaves the housing at the output end through the optical fibre duct. The treating laser light to be emitted from the fibre output end is supplied by a laser in an apparatus that is connected to the fibre so that light from the laser is coupled into the fibre.
When treating laser light is emitted from the fibre output end, a spray coolant of mixed air and water is simultaneously emitted from the output end of the handpiece housing providing cooling of tissue surrounding the treated area illuminated by the laser light. Thus, the apparatus further comprises a water control member that is adapted to be interconnected between a water supply and the water duct and to control the amount of water flowing into the water duct, and an air control member that is adapted to be interconnected between a supply of compressed air and the air duct and to control the amount of compressed air flowing into the air duct.
The apparatus also has a controller for controlling the operation of the system and being connected to the water control member and the air control member and being adapted to set the amount of water flowing into the water duct in the range from 5 ml/min to 50 ml/min, preferably from 10 ml/min to 30 ml/min, and more preferred to approximately 20 ml/min.
Further the controller is adapted to set the pressure of compressed air flowing into the air duct so that a coolant spray of mixed air and water is formed. This may be done by provision of a user interface that is connected to the controller and that is utilised by an operator of the system to enter parameter values of the system to be set by the controller. The operator may in this way increase the pressure of compressed air until formation of the spray of mixed air and water is visually detected.
The amount of water forming the water spray is selected so that the amount is sufficient to effectively cool surrounding tissue not to be treated by the laser light while being less than an amount that would absorb so much laser light that treatment would be inhibited.
According to an important aspect of the present invention, the wavelength and the power level of the laser light are selected so that only matter that abuts the fibre output end is heated when illuminated by the laser light. Thus, there is no risk of harming tissue that is accidentally illuminated by laser light emitted from the fibre output end as the energy density in the emitted laser light decreases rapidly with distance from the fibre output end.
According to another important aspect of the present invention, efficient cooling of tissue surrounding target area being treated by the laser light is provided by directing a coolant spray of air and water towards the surroundings of the fibre output end. As the water leaves the housing through the fibre duct and at least some of the water continues to flow along the surface of the fibre, accurate directing of the air and water spray along a longitudinal axis of the fibre is provided. The amount and composition of the air and water spray and the amount of light energy supplied to the treatment area are selected so that efficient cooling of the surroundings of the treatment area is provided thereby effectively preventing conduction of heat from the treatment area while simultaneously raising the temperature of matter abutting the fibre output end sufficiently to destroy and preferably remove the matter.
Light of 1 xcexcm wavelengths are moderately absorbed in water and the extinction length in soft tissue is about 1 to 3 mm. However, colour and structure of tissue have a great influence on absorption of light in this wavelength range and pigmented tissue absorbs light in this wavelength range efficiently. The light is for example absorbed in blood causing photocoagulation of blood and this effect is advantageously utilised during treatments with the present system.
Typically, the treatment is initiated when the fibre output end accumulates dark particles that is heated through light absorption. Plasma, a super-heated gas, may form on the surface abutting the fibre output end. Plasma absorbs the light and conducts heat to the matter to be treated, such as gingival tissue, plaque, calculus, etc. Plaque and tissue to be treated typically evaporates and calculus becomes brittle during treatment.
It should be recognised that many parameters of the treating light determine the effect of the treatment. Such parameters comprise the laser wavelength, laser power, laser waveform, tissue optical properties, tissue thermal properties, way of cooling, etc. The number of possible combinations of these parameters is infinite, many of which would result in inefficient treatment and/or unacceptable damage to tissue that should not be treated. Thus, the present invention is based on intensive research and clinical tests in the field of treatment of periodontal pockets using laser light.
As will be described in more detail below, this intensive research has revealed that it is possible to effectively treat periodontal pockets without damaging healthy tissue with a system according to the present invention.
The combination of average power in the emitted light and the repetition rate of emitted light pulses has to be set in a power range and a frequency range, respectively, wherein the above-mentioned thermal effects occur without a risk of damaging healthy tissue. It has been found that treatment with repetition frequencies below 50 Hz has resulted in unsatisfactory clinical results and that repetition frequencies below 70 Hz can be safely utilised without heating surrounding tissue at average power levels ranging from 1 to 10 W. Preferably the average power ranges from 3 W to 8 W. For pocket curettage it is preferred to set the average power ranging from 4 W to 6 W, and most preferred the average power is approximately 5 W and for laser surgery it is preferred to set the average power ranging from 5 W to 8 W, and more preferred from 6 W to 7 W.
The repetition frequency preferably ranges from 50 Hz to 70 Hz, more preferred from 55 Hz to 65 Hz, and still more preferred the repetition frequency is approximately 60 Hz.
Simultaneously, the duration of the light pulses must be within the range wherein sufficient energy is delivered to effectively heat matter to be treated without the average power attaining unsafe levels. According to the present invention it is preferred that the duration of the light pulses ranges from 150 xcexcs to 500 xcexcs, preferably from 200 xcexcs to 300 xcexcs, more preferred that the duration is approximately 250 xcexcs.
It is an important advantage of the present invention that the emitted laser light causes photocoagulation of blood so that possible bleeding of treated tissue is quickly stopped.
The laser may be any laser capable of emitting light of suitable wavelength and with sufficient power for illuminated matter to be treated, such as Nd YAG lasers, NCG lasers, diode lasers, etc.
A Nd YAG laser emits light at a wavelength of 1.064 xcexcm. The Nd YAG laser is particularly well suited as a light source in a dental system for treatment of periodontal pockets as water has a moderate energy absorbance at 1.064 xcexcm so that heating of matter abutting the fibre output end is provided while simultaneously allowing water in the coolant spray impeding on surrounding matter to effectively cool the surroundings of the matter being treated. Further, the Nd YAG laser is capable of reliably delivering the required laser power.
The optical fibre of the handpiece according to the present invention may be any fibre, such as an optical fibre made of pure silica, etc, that is suitable for transmission of light emitted from the laser and that is made of a material that allows repeated bending of the fibre so that an operator can freely manipulate the handpiece, e.g., in order to insert the fibre output end into a periodontal pocket of a patient. It is preferred that the outer diameter of the fibre ranges from 300 xcexcm to 600 xcexcm, and presently it is preferred to use fibres with an outer diameter of approximately 400 xcexcm or approximately 600 xcexcm.
For an operator of the system to be able to treat a suitable area during a suitable time period, it is presently preferred that the laser is adapted to emit light for a period ranging from 10 s to 1 minutes upon user activation, and more preferred for a period ranging from 20 s to 50 s upon user activation, and even more preferred for a period of approximately 30 s upon user activation.
The user interface may comprise a foot pedal for activation of the system so that light is emitted from the fibre output end upon activation of the foot pedal.
The controller may comprise at least one timer for accumulation of the time during which light has been emitted by the system. A timer value may be displayed to the operator of the system on the user interface. The timer value may be utilised by the operator of the system for calculation of cost of a treatment.
A timer value may be read by a service technician during maintenance of the system, e.g., in order to decide whether preventive service tasks have to be performed or not.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.